I came across a series of youtube videos of a
class Dr. Ingham taught in Hawaii in 2012. A five day
course, I think it is close to twenty hours of her talking about the soil food web, what makes it up, how to measure it, what it does, how to get it balanced. I have not finished listening to the first day yet and it is already close to information overload
Tree
roots gorwing 250 feet and more down into the ground, and transferring dye from the trunks above ground down 250 feet into the ground in about three minutes. Grasses with roots twenty feet deep. Lots of astonishing stuff, and lots of really useful stuff.